Ignition misfire/ dyno tuning question

[csx289]

Greetings-

I have an odd problem with my 06 GT that I am hoping some of you have experience with, more specifically, experience AND a cure! :lol

My car was taken to a very experienced high-performance Ford tech for a dyno tune. 16 year Ford master tech who opened his own shop to do mods such as this, and a really sharp guy. He is an SCT dealer. My car, bone stock except for K&N filters and a FRPP muffler, with 700 miles on it, misfired like crazy on the first pull. The dyno graph showed an extremely ragged HP curve, and at about 5500 it fell on its face, with really bad misfiring. 454 HP at the wheels, quite dismal IMHO. Having seen problems like this before with high boost and platinum plugs, the tech swapped in copper plugs gapped down. The misfire was far less noticable, and the car picked up about 50 hp and held its lunch until about 6k. We continued with the install of a 2.7 pulley and an SCT tune. The car made around 590 hp and still had a misfire. A/F is nice and steady, on the safe side at 12:1 +/- as I recall. There is a lean spike on tip in down low, but that is common I presume. I still have a misfire you can feel on the dyno, the car literally bucks.

We swapped in a set of known-good ignition coils, no change. We swapped in a new crank position sensor, no change. I had the local Ford hacks do a series of tests but all they suceeded in doing was scratching my door, hood, and door sill. :thumbsdow

I now have about 1700 miles on the car, and it runs well, but I know it could run a heck of a lot better without the spark issue. Last dyno pull was 608 HP and 570 ft lbs tq. (+/-, don't have the sheet here).

Obviously, I would like to solve this soon as I am planning a 2000 mile road trip to VIR for the Shelby club convention in 2 weeks. Well, I'd like to solve this and about 5 other problems like the "rattlesnake" noise in the dash and the like...but the misfire is the most troubling and pressing issue.

Any help or advice you can offer would be much appreciated.

Best regards,
Colin

 

[tmcphail]

And the current plug gap is what ?

 

[csx289]

I think the current plug gap is .025"....but I could be wrong - my memory isn't what it used to be

We compared the dyno graphs to other cars tuned on this dyno, at this shop - like a big HP 03 Cobra. The misfire and ragged power curve on the GT is clearly evident compared to other cars without this misfire issue.

Maybe I should just buy an 03 SVT Cobra? At least they have a trunk. :biggrin

Colin

 

[tmcphail]

@ .025 it should not blow out at hi RPM. I have mine at .030 and its nice and smooth thru the whole range. What exact brand / PN plug are you running ?

 

[csx289]

I'll get the exact plug info tomorrow. Remember, with the stock plugs at stock gap it was terrible...I don't think the plugs are the issue. It seems like the coils are picking up RF or just losing juice. A "boost-a-spark" was mentioned as a possible cure, but I know many others are not using this device and do not have the problem.

 

[tmcphail]

Increase cylinder pressure with more boost + stock gap = blow out. Mine was cured with a regap but you have done that already. Given the HP level you shouldn't have any problems. So something must be afoot.

 

[csx289]

Agreed. If anybody has any dyno sheets they could share to compare to mine it would be much appreciated. My email is colin@colinsclassicauto.com
I would like to have as much info possible to show to a buddy from Ford so he can see the problem.

Anybody used the Boost a Spark? My only concern is there is obvioulsy a problem that has been masked but not cured by copper plugs gapped down. My baseline runs stock should have been a lot better I would have thought.

Thanks,
Colin

 

[AMB]

csx289

You might check the Supercharger/TB inlet for "OIL" !! When I changed my TB, it had OIL in the inlet and the TB had a lot of baked carbon on it !! I changed the TB with ONLY 500 miles on it. Your 12:1 A/F is TOO LEAN for the boost you are running; It should be at least 11.5:1 !!! There are other things that should be changed in the TUNE to HELP your PROBLEMS !!!

AMB

 

[californiacuda]

I wonder if csx289 has fixed his problem? Is it possible the throttle body inlet boot is collapsing, causing reduced air flow at higher loads?

 

[Silverbullitt]

I wonder if csx289 has fixed his problem? Is it possible the throttle body inlet boot is collapsing, causing reduced air flow at higher loads?

ditto and watch a/f carefully. You need to run rich under load for a boosted application. This bites, but the excess fuel is used to cool the charge to prevent detonation. I learned this from my 03 cobra.

 

[csx289]

Hey guys,
Nope, not fixed yet - haven't got together with the factory engineer to drag him to the dyno yet.

Intake boot is not the culprit, and a/f is spot on (albeit a lot richer than I like, but very safe!). It is an ignition misfire and it is quite evident from 3,000 rpm where we start the pull to 6500 where we stop. As previously mentioned, it was far worse with the factory plugs, no tune, no pulley - as the car was delivered from Ford. So something is wrong in there, just don't know what yet!

Surely I can't be the only one with this issue? Please???? Karma is a bitch. LOL

Colin

 

[tmcphail]

Can you post a graph ?

 

[californiacuda]

Torrie, what mods have u done to your car? Nice rwhp.

 

[tmcphail]

2.7 and my tune. I actually got a much better graph out of my car tonight to the tune of 677RWHP

Mr. Torrie R. McPhail
2005 Ford GT Black / Silver stripe 618rwhp / 592 rwtq
2005 Silver Viper 490rwhp / 530rwtq
150 shot 610 rwhp / 760 rwtq
2006 Silver Jeep SRT-8 12.5@109.6

 

[californiacuda]

How is that possible? Are you using race fuel and aggressive timing advance?

 

[tmcphail]

No just a little chemical intercooling :wink

 

[californiacuda]

Nitrous or methanol

 

[tmcphail]

the big N ! :biggrin

Mr. Torrie R. McPhail
2005 Ford GT Black / Silver stripe 618rwhp / 592 rwtq
2005 Silver Viper 490rwhp / 530rwtq
150 shot 610 rwhp / 760 rwtq
2006 Silver Jeep SRT-8 12.5@109.6

 

[californiacuda]

I have an Audi rs6, comes from the factory with twin turbo v8(450 hp). I put a 150 shot of nitrous on it and I have had no problems. The big worry on the Audi is the transmission.

I spoke with Manley(the Gt rod maker), they said the rods and pistons can take 1000hp. The supercharger uses almost 150 hp, so you can add alot more "help" and as long as the engine doesn't get to lean.

I'm putting twin turbos on my car right now and were going to inch up to 1000 hp.

 

[tmcphail]

That was a 50 shot set up very conservative. And I am wholly familiar with these cars. I have had a hand in the drivability tuning on Joes TT GT and am good friends with him, HP and the guys at stage 6. Making HP for a living and hanging out in this crowd makes it extremely hard to say no to TT's on my personal car let me tell ya.

It is Joe's fault I bought this car in the first place. That fateful Sunday when his car was in the mid 800rwhp range joe was nice enough to let me go for a ride. My life changed that instant. 5 days later I bought my GT.

Mr. Torrie R. McPhail
2005 Ford GT Black / Silver stripe 618rwhp / 592 rwtq
2005 Silver Viper 490rwhp / 530rwtq
150 shot 610 rwhp / 760 rwtq
2006 Silver Jeep SRT-8 12.5@109.6